Russian Cyberspies Use UEFI Rootkit in Attacks

Russian cyber-espionage group Fancy Bear is the first threat actor to have used a Unified Extensible Firmware Interface (UEFI) rootkit in a malicious campaign, ESET’s security researchers claim.

Several years ago, Italy-based surveillance software maker Hacking Team was said to have used a UEFI rootkit to ensure the persistence of its software on targeted systems, but no UEFI rootkit had “ever been detected in the wild,” the security firm claims.

A recently discovered Fancy Bear campaign, however, changes that: the actor was able to successfully deploy a malicious UEFI module on a victim’s system. Not only does this prove that UEFI rootkits are a real threat, but also shows that Fancy Bear may be even more dangerous than thought, ESET says.

Active for the past decade and a half, the actor, which is also referred to as APT28, Strontium, Sofacy and Sednit, is believed to have orchestrated a variety of high profile attacks, such as the DNC hack before the US 2016 elections.

Earlier this year, after the group’s Zerbrocy malware was found on systems infected with Turla’s Mosquito backdoor, security researchers concluded that the threat actor’s activities overlap with other state-sponsored operations.

“Our investigation has determined that this malicious actor was successful at least once in writing a malicious UEFI module into a system’s SPI flash memory. This module is able to drop and execute malware on disk during the boot process. This persistence method is particularly invasive as it will not only survive an OS reinstall, but also a hard disk replacement,” ESET reveals in a report published today.

In May, Fancy Bear was revealed to have abused LoJack (a Trojanized version of the tool, which ESET calls LoJax) in their attacks. Deeper analysis of the campaign revealed not only that the actor attempted to mimic the tool’s persistence method, but also that additional tools were used for accessing and modifying UEFI/BIOS settings.

These include a kernel driver and three tools to (1) dump information about low level system settings, (2) save an image of the system firmware, and (3) add a malicious UEFI module to the image. The third tool would then write the modified firmware image back to the SPI flash memory, thus effectively installing the UEFI rootkit on the system.

“If the platform allows write operations to the SPI flash memory, it will just go ahead and write to it. If not, it actually implements an exploit against a known vulnerability,” ESET reveals.

The UEFI rootkit was designed to drop malware onto the Windows operating system partition and make sure that it is executed at startup.

The observed LoJax samples used command and control (C&C) servers previously associated with Fancy Bear’s SedUploader first-stage backdoor, which, combined with the presence of other Sednit tools on LoJax-infected machines (SedUploader, XAgent backdoor, and Xtunnel network proxy tool), suggested that this threat actor was behind the attacks.

Sednit’s UEFI rootkit, ESET discovered, is not properly signed, meaning that Secure Boot would be able to block it. The security researchers also note that the attack can write the modified firmware image only if SPI flash memory protections are vulnerable or misconfigured.

“The LoJax campaign shows that high-value targets are prime candidates for the deployment of rare, even unique threats and such targets should always be on the lookout for signs of compromise. Also, one thing that this research taught us is that it is always important to dig as deep as you can go!” ESET concludes.